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The early history of the Airplaneo
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EARLY Ht/TORY
• Or fne • •
AIRPLANE
OAYTON-WRIGHT AIRPLANE Oa
OAYTON*OHIO
LIBRARY
UNIVERSITY OF CALIFORNIA
DAVIS
Digitized by the Internet Archive
in 2007 with funding from
IVIicrosoft Corporation
http://www.archive.org/details/earlyhistoryofaiOOwrigrich
The IDright Brothers' Aeroplane
By OrvilU and Wilbur Wright
^ m I >HOUGH the subject of aerial
Y l"^ navigation is generally consid-
\^j J ered new, it has occupied the
^^ minds of men more or less
from the earliest ages. Our personal in-
terest in it dates from our childhood
days. Late in the autumn of 1878 our
father came into the house one evening
with some object partly concealed in his
hands, and before we could see what it
was, he tossed it into the air. Instead of
falling to the floor, as we expected, it flew
across the room, till it struck the ceiling,
where it fluttered awhile, and finally
sank to the floor. It was a little toy,
known to scientists as a "helicoptere,"
but which we, with sublime disregard for
science, at once dubbed a "bat." It was
a light frame of cork and bamboo, cov-
ered with paper, which formed two
screws, driven in opposite directions by
rubber bands under torsion. A toy so
delicate lasted only a short time in the
hands of small boys, but its memoiy was
abiding.
Several years later we began building
these helicop teres for ourselves, making
each one larger than that preceding. But,
to our astonishment, we found that the
larger the "bat" the less it flew. Wejlid
noMaixDw^tlial^^^nachir^^ only
twicejhe Imear dimensions of another
wouldrgguire^ightjtimes the power. We
finally became discouragedTandreturned
to kite-flying, a sport to which we had de-
voted so much attention that we were
regarded as experts. But as we became
older we had to give up this fascinating
sport as unbecoming to boys of our ages.
It was not till the news of the sad death
of Lilienthal reached America in the
summer of 1896 that we again gave more
than passing attention to the subject of
flying. We then studied with great in-
terest Chanute's "Progress in Flying Ma-
chines," Langley's "Experiments in
Aerodynamics," the "Aeronautical An-
nuals" of 1905, 1906, and 1907, and sev-
eral pamphlets published by the Smith-
sonian Institution, especially articles by
Lilienthal and extracts from Mouillard's
"Empire of the Air." The larger works
gave us a good understanding of the na-
ture of the flying problem, and the diffi-
culties in past attempts to solve it, while
Mouillard and Lilienthal, the great mis-
sionaries of the flying cause, infected us
with their own unquenchable enthusi-
asm, and transformed idle curiosity into
the active zeal of workers.
In the field of aviation there were two
schools. The first, represented by such
men as Professor Langley and Sir Hiram
Maxim, gave chief attention to power
flight; the second, represented by Lilien-
thal, Mouillard, and Chanute, to soaring
flight. Our sympathies were with the
latter school, partly from impatience at
the wasteful extravagance of mounting
delicate and costly machinery on wings
which no one knew how to manage, and
partly, no doubt, from the extraordinary
charm and enthusiasm with which the
apostles of soaring flight set forth the
beauties of sailing through the air on
fixed wdngs, deriving the motive power
from the wind itself.
The balancing of a flyer may seem, at
first thought, to be a very simple matter,
yet almost ever>' experimenter had found
in this one point which he could not sat-
isfactorily master. Many diflerent meth-
LIBRARV
UNIVERSITY OF CALIFORNIA
DAVIS
THE
EARLY
HISTORY
O F
THE
AIRPLANE
ods were tried. Some experimenters
placed the center of gravity far below
the wings, in the belief that the weight
would naturally seek to remain at the
lowest point. It is true, that, like the
pendulum, it tended to seek the lowest
point; but also, like the pendulum, it
tended to oscillate in a manner destruc-
tive of all stability. A more satisfactory
system, especially for lateral balance,
was that of arranging the wings in the
shape of a broad V, to form a dihedral
angle, with the center low and the wing-
tips elevated. In theory this was an au-
tomatic system, but in practice it had two
serious defects: first, it tended to keep
the machine oscillating; and second, its
usefulness was restricted to calm air.
In a slightly modified form the same
system was applied to the fore-and-aft
balance. The main aeroplane was set at
a positive angle, and a horizontal tail at
a negative angle, while the center of
gravity was placed far forward. As in
the case of lateral control, there was a
tendency to constant undulation, and the
very forces which caused a restoration
of balance in calms caused a disturbance
of the balance in winds. Notwithstand-
ing the known limitations of this prin-
ciple, it had been embodied in almost
every prominent flying machine which
had been built.
After considering the practical effect
of the dihedral principle, we reached the
conclusion that a flyer founded upon it
might be of interest from a scientific
point of view, but could be of no value
in a practical way. We therefore re-
solved to try a fundamentally different
principle. We would arrange the ma-
chine so that it would not tend to right
itself. We would make it as inert as
possible to the effects of change of direc-
tion or speed, and thus reduce the effects
of wind-gusts to a minimum. We would
do this in the fore-and-aft stability by
giving the aeroplanes a peculiar shape;
and in the lateral balance by arching the
surfaces from tip to tip, just the reverse
of what our predecessors had done. Then
by some suitable contrivance, actuated
by the operator, forces should be brought
into play to regulate the balance.
Lilienthal and Chanute had guided and
balanced their machines, by shifting the
weight of the operator's body. But this
method seemed to us incapable of ex-
pansion to meet large conditions, be-
cause the weight to be moved and the
distance of possible motion were limited,
while the disturbing forces steadily in-
creased, both with wing area and with
wind velocity. In order to meet the
needs of large machines, we wished to
employ some system whereby the oper-
ator could vary at will the inclination of
different parts of the wings, and thus ob-
tain from the wind forces to restore the
balance which the wind itself had dis-
turbed. This could easily be done by
Using wings capable of being warped, and
by supplementary adjustable surfaces in
the shape of rudders. As the forces ob-
tainable for control would necessarily
increase in the same ratio as the disturb-
ing forces, the method seemed capable of
expansion to an almost unlimited extent.
A happy device was discovered whereby
the apparently rigid system of super-
posed surfaces, invented by Wenham,
and improved by Stringfellow and
Chanute, could be warped in a most un-
expected way, so that the aeroplanes
could be presented on the right and left
sides at different angles to the wind.
This, with an adjustable, horizontal front
rudder, formed the main feature of our
first glider.
The period from 1885 to 1900 was one
of unexampled activity in aeronautics,
and for a time there was high hope that
the age of flying was at hand. But Max-
im, after spending $100,000, abandoned
THE
EARLY
HISTORY
O F
THE
AIRPLANE
the work; the Ader machine, built at the
expense of the French Government, was
a failure; Lilienthal and Pitcher were
killed in experiments; and Chanute and
many others, from one cause or another,
had relaxed their efforts, though it sub-
sequently became known that Professor
Langley was still secretly at work on a
machine for the United States Govern-
ment. The public, discouraged by the
failures and tragedies just witnessed,
considered flight bej'ond the reach of
man, and classed its adherents with the
inventors of perpetual motion.
We began our active experiments at
the close of this period, in October, 1900,
at Kitty Hawk, North Carolina. Our ma-
chine was designed to be flown as a kite,
with a man on board, in winds from 15
to 20 miles an hour. But, upon trial, it
was found that much stronger winds
were required to lift it. Suitable winds
not being plentiful, we found it neces-
sary, in order to test the new balancing
system, to fly the machine as a kite with-
out a man on board, operating the levers
through cords from the ground. This
did not give the practice anticipated, but
it inspired confidence in the new system
of balance.
In the summer of 1901 we became per-
sonally acquainted with Mr. Chanute.
When he learned that we were interested
in flying as a sport, and not with any ex-
pectation of recovering the money we
were expending on it, he gave us much
encouragement. At our invitation, he
spent several weeks with us at our camp
at Kill Devil Hill, four miles south of
Kitty Hawk, during our experiments of
that and the two succeeding years. He
also witnessed one flight of the power
machine near Dayton, Ohio, in October,
1904.
The machine of 1901 was built with
the shape of surface used by Lilienthal,
curved from front to rear like the seg-
ment of a parabola, with a curvature
1/12 the depth of its cord; but to make
doubly sure that it would have sufficient
lifting capacity when flown as a kite in
15 or 20-mile winds, we increased the
area from 165 square feet, used in 1900,
to 308 square feet — a size much larger
than Lilienthal, Pitcher, or Chanute had
deemed safe. Upon trial, however, the
lifting capacity again fell very far short
of calculation, so that the idea of secur-
ing practice while flying as a kite had to
be abandoned. Mr. Chanute, who wit-
nessed the experiments, told us that the
trouble was not due to poor construction
of the machine. We saw only one other
explanation — that the tables of air-pres-
sures in general use were incorrect.
We then turned to gliding — coasting
downhill on the air — ^as the only method
of getting the desired practice in balanc-
ing a machine. After a few minutes'
practice we were able to make glides of
over 300 feet, and in a few days were
safely operating in 27-mile winds. In
these experiments we met with several
unexpected phenomena. We found that,
contrary to the teachings of the books,
the center of pressure on a curved sur-
face traveled backward when the surface
was inclined, at small angles, more and
more edgewise to the wind. We also dis-
covered that in free flight, when the wing
on one side of the machine was presented
to the wind at a greater angle than the
one on the other side, the wing with the
greater angle descended, and the machine
turned in a direction just the reverse of
THE
EARLY
HISTORY
O F
THE
AIRPLANE
what we were led to expect when flying
the machine as a kite. The larger angle
gave more resistance to forward motion,
and reduced the speed of the wing on
that side. The decrease in speed more
than counterbalanced the eflect of the
larger angle. The addition of a fixed
vertical vane in the rear increased the
trouble, and made the machine absolute-
ly dangerous. It was some time before
a remedy was discovered. This consisted
of movable rudders working in conjunc-
tion with the twisting of the wings. The
details of this arrangement are given in
specifications published several years
ago.
The experiments of 1901 were far
from encouraging. Although M r .
Chanute assured us that, both in control
and in weight carried per horse-power,
the results obtained were better than
those of any of our predecessors, yet we
saw that the calculations upon which all
flying machines had been based were un-
reliable, and that all were simply groping
in the dark. Having set out with abso-
lute faith in the existing scientific data,
we were driven to doubt one thing after
another, till finally, after two years of
experiment, we cast it all aside, and de-
cided to rely entirely upon our own in-
vestigations. Truth and error were
everywhere so intimately mixed as to be
undistinguishable. Nevertheless, the
time expended in preliminary study of
books was not misspent, for they gave us
J a good general understanding of the sub-
ject, and enabled us at the outset to avoid
effort in many directions in which re-
sults would have been hopeless.
The standard measurements of wind-
pressures is the force produced by a cur-
rent of air of one mile per hour velocity
striking square against a plane of one
square foot area. The practical difficul-
ties of obtaining an exact measurement
of this force have been great. The meas-
/
urements by different recognized author- /
ities vary 50 i^er cent. When this simp-
lest of measurements presents so great
difficulties, what shall be said of the
troubles encountered by those who at-
tempt to find the pressure at each angle
as the plane is inclined more and more
edgewise to the wind? In the eighteenth
centui*y the French Academy prepared
tables giving such information, and at a
later date the Aeronautical Society of
Great Britain made similar experiments.
Manj' persons likewise published meas-
urements and formulas; but the results
were so discordant that Professor Lang-
ley undertook a new series of measure-
ments, the results of which form the
basis of his celebrated work, "Experi-
ments in Aerodynamics." Yet a critical
examination of the data upon which he
based his conclusions as to the pressures
at small angles shows results so various
as to make many of his conclusions little
better than guesswork.
To work intelligently, one needs to
know the effects of a multitude of varia-
tions that could be incorporated in the
surfaces of flying machines. The pres-
sures on squares are different from
those on rectangles, circles, triangles, or
ellipses; arched surfaces differ from
planes, and vary among themselves ac-
cording to the depth of cur\'ature; true
arcs differ from parabolas, and the latter
differ among themselves; thick surfaces
differ from thin, and surfaces thicker in
one place than another vary in pressure
when the positions of maximum thick-
ness are difterent; some surfaces are
most efficient at one angle, others at other
angles. The shape of the edge also makes
a difference, so that thousands of com-
binations are possible in so simple a
thing as a wing.
We had taken up aeronautics merely
as a sport. We reluctantly entered upon
the scientific side of it. But we soon
THE
EARLY
HISTORY
O F
THE
AIRPLANE
found the work so fascinating that we
were drawn into it deeper and deeper.
Two testing machines were built, which
we believed would avoid the errors to
which the measurements of others had
been subject. After making preliminary
measurements on a great number of dif-
ferent-shaped surfaces, to secure a gen-
eral understanding of the subject, we be-
gan systematic measurements of stan-
dard surfaces, so varied in design as to
bring out the underlying causes of dif-
ferences noted in their pressures. Meas-
urements were tabulated on nearly 50 of
these at all angles from zero to 45 de-
grees at intervals of 2i/2 degrees. Meas-
urements were also secured showing the
effects on each other when surfaces are
superposed, or when they follow one an-
other.
Some strange results were obtained.
One surface, with a heavy roll at the
front edge, showed the same lift for all
angles from 7I/2 to 45 degrees. A square
plane, contrary to the measurements of
all our predecessors, gave a greater pres-
sure at 30 degrees than at 45 degrees.
This seemed so anomalous that we were
almost ready to doubt our own measure-
ments, when a simple test was suggested.
A weather-vane, with two planes attached
to the pointer at an angle of 80 degrees
with each other, was made. According
to our tables, such a vane would be in
unstable equilibrium when pointing di-
rectly into the wind; for if by chance the
wind should happen to strike one plane
at 39 degrees and the other at 41 degrees,
the plane with the smaller angle would
have the greater pressure, and the pointer
would be turned still farther out of the
course of the wind until the two vanes
again secured equal pressures, which
would be at approximately 30 and 50 de-
grees. But the vane performed in this
very manner. Further corroboration of
the tables was obtained in experiments
with the new glider at Kill Devil Hill the
next season.
In September and October, 1902, near-
ly 1,000 gliding flights were made, sev-
eral of whicli covered distances of over
600 feet. Some, made against a wind of
36 miles an hour, gave proof of the ef-^
fectiveness of the devices for control.
With this machine, in the autumn of
1903, we made a number of flights in
which we remained in the air for over a
minute, often soaring for a considerable
time in one spot, without any descent at
all. Little wonder that our unscientific
assistant should think the only thing
needed to keep it indefinitely in the air
would be a coat of feathers to make it
light!
With accurate data for making calcu-
lations, and a system of balance effective
in winds as well as in calms, we were
now in a position, we thought, to build a
successful power-flyer. The first designs
provided for a total weight of 600 lbs., in-
cluding the operator and an eight horse-
power motor. But, upon completion, the
motor gave more power than had been
estimated, and this allowed 150 lbs. to be
added for strengthening the wings and
other parts. ,
Our tables made the designing of the
wings an easy matter, and as screw-
propellers are simply wings traveling in
a spiral course, we anticipated no trouble
from this source. W^e had thought of
getting the theory of the screw-propeller
from the marine engineers, and then, by
applying our tables of air-pressures to
their formulas, of designing air-propel-y
lers suitable for our purpose. But so far
as we could learn, the marine engineers
possessed only empirical formulas, and
the exact action of the screw-propeller,
after a century of use, was still very ob-
scure. As we were not in a position to
undertake a long series of practical ex-
periments to discover a propeller suitable
THE
EARLY
HISTORY
O F
THE
AIRPLANE
for our machine, it seemed necessary to
obtain such a thorough understanding
of the theory of its reactions as would
enable us to design them from calcula-
tions alone. What at first seemed a prob-
lem became more complex the longer we
studied it. With the machine moving
forward, the air flying backward, the
propellers turning sidewise, and nothing
standing still, it seemed impossible to find
a starting-point from which to trace the
various simultaneous reactions. Con-
templation of it was confusing. After
long arguments we often found our-
selves in the ludicrous position of each
having been converted to the other's side,
with no more agreement than when the
discussion began.
It was not till several months had
passed, and every phase of the problem
had been thrashed over and over, that
the various reactions began to untangle
themselves. When once a clear under-
standing had been obtained there was no
difficulty in designing suitable propellers,
with proper diameter, pitch, and area of
blade, to meet the requirements of the
flyer. High eflQciency in a screw-propel-
ler is not dependent upon any particular
or peculiar shape; and there is no such
thing as a "best" screw. A propeller giv-
ing a high dynamic efficiency when used
upon one machine may be almost worth-
less when used upon another. The
propeller should in every case be
designed to meet the particular condi-
tions of the machine to which it is to be
applied. Our first propellers, built en- .
tirely from calculation, gave in useful ^
work 66 per cent, of the power expended.
This was about one-third more than had
been secured by Maxim or Langley.
The first flights with the power ma-
chine were made on December 17, 1903.
Only five persons besides ourselves were
present. These were Messrs. John T.
Daniels, W. S. Dough, and A. D. Ether-
idge, of the Kill Devil Life-Saving Sta-
tion; Mr. W. C. Brinkley, of Manteo; and
Mr. John Ward, of Naghead. Although
a general invitation had been extended
to the people living within five or six
miles, not many were willing to face the
rigors of a cold December wind in order
to see, as they no doubt thought, another
flying machine not fly. The first flight
lasted only 12 seconds, a flight very mod-
est compared with that of birds, but it
was, nevertheless, the first in the history
of the world in which a machine carry-
ing a man had raised itself by its own
power into the air in free flight, had
saileed forward on a level course without
reduction of speed, and had finally land-
ed without being wrecked. The second
and third flights were a little longer, and
the fourth lasted 59 seconds, covering a
distance of 852 feet over the ground
against a 20-mile wind.
After the last flight the machine was
carried back to camp and set down in
what was thought to be a safe place. But
a few minutes later, while we were en-
gaged in conversation about the flights, a
sudden gust of wind struck the machine,
and started to turn it over. All made a
rush to stop it, but we were too late.
Mr. Daniels, a giant in stature and
strength, was lifted off his feet, and fall-
ing inside, between the surfaces, was
THE
EARLY
HISTORY
O F
THE
AIRPLANE
shaken about like a rattle in a box as the
machine rolled over and over. He finally
fell out upon the sand with nothing worse
than painful bruises, but the damage to
the machine caused a discontinuance of
experiments.
In the spring of 1904, through the
kindness of Mr. Torrence Huffman, of
Daj'ton, Ohio, we were permitted to erect
a shed, and to continue experiments, on
what is known as the Huffman Prairie,
at Simms Station, eight miles east of Day-
ton. The new machine was heavier and
stronger, but similar to the one flown at
Kill Devil Hill. When it was ready for
its first trial every newspaper in Dayton
was notified, and about a dozen represen-
tatives of the Press were present. Our
only request was that no pictures be
taken, and that the reports be unsensa-
tional, so as not to attract crowds to our
experiment grounds. There were prob-
ably 50 persons altogether on the ground.
When preparations had been completed
a wind of only three or four miles was
blowing — insufficient for starting on so
short a track — but since many had come
a long way to see the machine in action,
an attempt was made. To add to the
other difficulty, the engine refused to
work properly. The machine, after run-
ning the length of the track, slid off the
end without rising into the air at all.
Several of the newspaper men returned
the next day, but were again disappoint-
ed. The engine performed badly, and
after a glide of only 60 feet, the machine
came to the ground. Further trial was
postponed till the motor could be put in
better running condition. The reporters
had now, no doubt, lost confidence in the
machine, though their reports, in kind-
ness, concealed it. Later, when they
heard that we were making flights of sev-
eral minutes' duration, knowing that
longer flights had been made with air-
ships, and not knowing any essential dif-
ference between airships and flying ma-
chines, they were but little interested.
We had not been flying long in 1904
before we found that the problem of
equilibrium had not as yet been entirely
solved. Sometimes, in making a circle,
the machine would turn over sidewise
despite anything the operator could do,
although, under the same conditions in
ordinary straight flight, it could have
been righted in an instant. In one flight,
in 1905, while circling around a honey
locust tree at a height of about 50 feet,
the machine suddenly began to turn up
on one wing, and took a course toward
the tree. The operator, not relishing the
idea of landing in a thorn-tree, attempted
to reach the ground. The left wing,
however, struck the tree at a height of 10
or 12 feet from the ground and carried
away several branches; but the flight,
which had already covered a distance of
six miles, was continued to the starting-
point.
The causes of these troubles — too tech-
nical for explanation here — ^were not en-
tirely overcome till the end of Septem-
ber, 1905. The flights then rapidly in-
creased in length, till experiments were
discontinued after October 5, on account
of the number of people attracted to the
field. Although made on a ground open
on every side, and bordered on two sides
by much-traveled thoroughfares, with
electric cars passing every hour, and seen
by aU the people living in the neighbor-
hood for miles around, and by several
hundred others, yet these flights have
been made by some newspapers the sub-
ject of a great "mystery."
A practical flyer having been finally
realized, we spent the years 1906 and
1907 in constructing new machines and
in business negotiations. It was not till
May of this year that experiments (dis-
continued in October, 1905) were re-
THE
EARLY
HISTORY
O F
THE
AIRPLANE
sumed at Kill Devil Hill, North Carolina.
The recent flights were made to test the
ability of our machine to meet the re-
quirements of a contract with the United
States Government to furnish a flyer
capable of carrying two men and sutli-
cient fuel supplies for a flight of 125
miles, with a speed of 40 miles an hour.
The machine used in these tests was the
same one with which the flights were
made at Simms Station in 1905, though
several changes had been made to meet
present requirements. The operator as-
sumed a sitting position, instead of lying
prone, as in 1905, and a seat was added
for a passenger. A larger motor was in-
stalled, and radiators and gasoline reser-
voirs of larger capacity replaced those
previously used. No attempt was made
to make high or long flights.
In order to show the general reader the
way in which the machine operates, let
us fancy ourselves ready for the start.
The machine is placed upon a single-rail
track facing the wind, and is securely
fastened with a cable. The engine is put
in motion, and the propellers in the rear
whir. You take j^our seat at the center
of the machine beside the operator. He
slips the cable, and you shoot forward.
An assistant who has been holding the
machine in balance on the rail starts for-
ward with you, but before you have gone
50 feet the speed is too great for him, and
he lets go. Before reaching the end of
the track the operator moves the front
rudder, and the machine lifts from the
rail like a kite supported by the pressure
of the air underneath it. The ground
under you is at first a perfect blur, but as
you rise the objects become clearer. At
a height of 100 feet you feel hardly any
motion at all, except for the wind which
strikes your face. If you did not take
the precaution to fasten your hat before
starting, you have probably lost it by
this time. The operator moves a lever:
the right wing rises, and the machine
swings about to the left. You make a
very short turn, yet you do not feel the
sensation of being thrown from your
seat, so often experienced in automo-
bile and railway travel. You find your-
self facing toward the point from which
you started. The objects on the ground
now seem to be moving at much higher
speed, though you perceive no change in
the pressure of the wind on your face.
You know then that you are traveling
with the wind. When you near the start-
ing-point the operator stops the motor
while still high in the air. The machine
coasts down at an oblique angle to the
ground, and after sliding 50 or 100 feet,
comes to rest. Although the machine
often lands when traveling at a speed of
a mile a minute, you feel no shock what-
ever, and cannot, in fact, tell the exact
moment at which it first touched the
ground. The motor close beside you
kept up an almost deafening roar during
the whole flight, yet in your excitement
you did not notice it till it stopped!
Our experiments have been conducted
entirelj' at our own expense. In the be-
ginning we had no thought of recovering
what we were expending, which was not
great, and was limited to what we could
afford in recreation. Later, when a suc-
cessful flight had been made with a mo-
tor, we gave up the business in which we
were engaged, to devote our entire time
and capital to the development of a ma-
chine for practical uses. As soon as our
condition is such that constant attention
to business is not required, we expect to
prepare for publication the results of our
laboratory experiments, which alone
made an early solution of the flying
problem possible.
liou? IPe Made the First Flight
By OrvilU Wright
.HE flights of the 1902 glider had
demonstrated the efficiency of
our system o f maintaining
equihbrium, and also the accu-
racy of the laboratory work upon which
the design of the glider was based. We
then felt that we were prepared to calcu-
late in advance the performance of ma-
chines with a degree of accuracy that had
never been possible with the data and
tables possessed by our predecessors.
Before leaving camp in 1902 we were al-
ready at work on the general design of a
new machine which we proposed to
propel with a motor.
Immediately upon our return to Day-
ton, we wrote to a number of automobile
and motor builders, stating the purpose
for which we desired a motor, and ask-
ing whether they could furnish one that
would develop eight brake-horsepower,
with a weight complete not exceeding 200
pounds. Most of the companies an-
swered that they were too busy with their
regular business to undertake the build-
ing of such a motor for us; but one com-
pany replied that they had motors rated
at 8 horse-power, according to the
French system of ratings, which weighed
only 135 pounds, and that if we thought
this motor would develop enough power
for our purpose they would be glad to
sell us one. After an examination of the
particulars of this motor, from which
we learned that it had but a single cylin-
der of 4-inch bore and 5-inch stroke, we
were afraid it was much over-rated.
Unless the motor would develop a full 8
brake-horsepower, it would be useless
for our purpose.
Finally we decided to undertake the
building of the motor ourselves. We es-
timated that we could make one of four
cylinders with 4-inch bore and 4-inch
stroke, weighing not over two hundred
pounds, including all accessories. Our
only experience up to that time in the
building of gasoline motors had been in
the construction of an air-cooled motor,
5-inch bore and 7-incli stroke, which was
used to run the machinery of our small
workshop. To be certain that four cylin-
ders of the size we had adopted (4" x 4")
would develop the necessary 8 horse-
power, we first fitted them in a tempor-
ary frame of simple and cheap construc-
tion. In just six weeks from the time the
design was started, we had the motor on
the block testing its power. The ability
to do this so quickly was largely due to
the enthusiastic and elTicient services of
Mr. C. E. Taylor, who did all the machine
work in our shop for the first as well as
the succeeding experimental machines.
There was no provision for lubricating
either cylinders or bearings while this
motor was running. For that reason it
was not possible to run it more than a
minute or two at a time. In these short
tests the motor developed about nine
horse-power. We were then satisfied
that, with proper lubrication and better
adjustments, a little more power could
THE
EARLY
HISTORY
O P
THE
AIRPLANE
be expected. The completion of the mo-
tor according to drawing was, therefore,
proceeded with at once.
While Mr. Taylor was engaged with
this work, Wilbur and I were busy in
completing the design of the machine
itself. The preliminary tests of the mo-
tor having convinced us that more than
8 horse-power would be secured, we felt
free to add enough weight to build a
more substantial machine than we had
originally contemplated.
******
For two reasons we decided to use two
propellers. In the first place we could,
by the use of two propellers, secure a re-
action against a greater quantity of air,
and at the same time use a larger pitch
angle than was possible with one propel-
ler; and in the second place by having the
propellers turn in opposite direction, the
gyroscopic action of one would neutral-
ize that of the other. The method we
adopted of driving the propellers in op-
posite directions by means of chains is
now too well known to need description
here. We decided to place the motor to
one side of the man, so that in case of a
plunge headfirst, the motor could not fall
upon him. In our gliding experiments
w^e had had a numbei- of experiences in
which we had landed upon one wing, but
the crushing of the wing had absorbed
the shock, so that we were not uneasy
about the motor in case of a landing of
that kind. To provide against the ma-
chine rolling over forward in landing, we
designed skids like sled runners, extend-
ing out in front of the main surfaces.
Otherwise the general construction and
operation of the machine was to be simi-
lar to that of the 1902 glider.
When the motor was completed and
tested, we found that it would develop 16
horse-power for a few seconds, but that
the power rapidlj^ dropped till, at the end
of a minute, it was only 12 horse-power.
Ignorant of what a motor of this size
ought to develop, we were greatly pleased
with its performance. More experience
showed us that we did not get one-half
of the power we should have had.
With 12 horse-power at our command,
we considered that we could pennit the
weight of the machine with operator to
rise to 750 or 800 pounds, and still have
as much surplus power as we had orig-
inally allowed for in the first estimate of
550 pounds.
Before leaving for our camp at Kitty
Hawk we tested the chain drive for tlie
propellers in our shop at Dayton, and
found it satisfactory. We found, how-
ever, that our first propeller shafts,
which were constructed of heavy gauge
steel tubing, were not strong enough to
stand the shocks received from a gaso-
line motor with light fly wheel, although
they would have been able to ti'ansmit
three or four times the power uniformly
applied. We therefore built a new set of
shafts of heavier tubing, which we tested
and thought to be abundantly strong.
We left Dayton, September 23, and ar-
rived at our camp at Kill Devil Hill on
Friday, the 25th. We found there pro-
visions and tools, which had been ship-
ped by freight several weeks in advance.
The building, erected in 1901 and en-
larged in 1902, was found to have been
blown by a stonn from its foundation
posts a few months previously. While
we were awaiting the arrival of the ship-
ment of machinery and parts from Day-
ton, we were busy putting the old build-
ing in repair, and erecting a new build-
ing to serve as a workshop for assemb-
ling and housing the new machine.
Just as the building was being com-
pleted, the parts and material for the ma-
chines arrived simultaneously with one
of the worst storms that had visited Kitty
Hawk in years. The storm came on sud-
denly, blowing 30 to 40 miles an hour.
w
THE
EARLY
HISTORY
O F
THE
AIRPLANE
It increased during the night, and the
next day was blowing over 75 miles an
hour. In order to save the tar-paper
roof, we decided it would be necessary
to get out in this wind and nail down
more securely certain parts that were
especially exposed. When I ascended
the ladder and reached the edge of the
roof, the wind caught under my large
coat, blew it up around my head and
bound my arms till I was perfectly help-
less. Wilbur came to mj' assistance and
held down my coat while I tried to drive
the nails. But the wind was so strong I
could not guide the hammer and succeed-
ed in striking my fingers as often as the
nails.
The next three weeks were spent in
setting the motor-machine together. On
days with more favorable winds we
gained additional experience in handling
a flyer bj^ gliding with the 1902 machine,
which we had found in pretty fair condi-
tion in the old building, where we had
left it the year before.
Mr. Chanute and Dr. Spratt, who had
been guests in our camp in 1901 and
1902, spent some time with us, but neith-
er one was able to remain to see the test
of the motor-machine, on account of the
delays caused by trouble which devel-
oped in the propeller shafts.
While Mr. Chanute was with us, a good
deal of time was spent in discussion of
the mathematical calculations upon
which we had based our machine. He
informed us that, in designing machin-
ery, about 20 per cent, was usually al-
lowed for the loss in the transmission of
powej*. As we had allowed only 5 per
cent., a figure we had arrived at by some
crude measurements of the friction of
one of tlie cliains when carrying only a
very light load, we were much alanned.
More than the whole surplus in power al-
lowed in our calculations would, accord-
ing to Mr. Ghanute's estimate, be con-
sumed in friction in the driving chains.
After Mr. Ghanute's departure, we sus-
pended one of the drive chains over a
sprocket, hanging bags of sand on either
side of the sprocket of a weight approx-
imately equal to the pull that would be
exerted on the chains when driving the
propellers. By measuring the extra
amount of weight needed on one side to
lift the weight on the other, we calcu-
lated the loss in transmission. This indi-
cated that the loss of power from this
source would be only 5 per cent., as we
originally estimated. But while we
could see no serious error in this method
of determining the loss, we were very
uneasy until we had a chance to run the
propellers with the motor to see whether
we could get the estimated number of
turns.
The first run of the motor on the ma-
chine developed a flaw in one of the
propeller shafts which had not been dis-
covered in the test at Dayton. The shafts
were sent at once to Daj'ton for repair,
and were not received again until No-
vember 20, having been gone two weeks.
We immediately put them in the machine
and made another test. A new trouble
developed. The sprockets which were
screwed on the shafts, and locked with
nuts of opposite thread, persisted in com-
ing loose. After many futile attempts to
get them fast, we had to give it up for
that day, and went to bed much discour-
aged. However, after a night's rest, we
got up the next morning in better spirits
and resolved to try again.
While in the bicycle business we had
become well acquainted with the use of
hard tire cement for fastening tires on
the rims. We had once used it success-
fully in repairing a stop watch after sev-
eral watchsmiths had told us it could not
be repaired. If tire cement was good for
fastening the hands on a stop watch, why-
should it not be good for fastening the
u
THE
EARLY
HISTORY
O F
THE
AIRPLANE
sprockets on the propeller shaft of a fly-
ing machine? We decided to try it. We
heated the shafts and sprockets, melted
cement into the threads, and screwed
them together again. This trouble was
over. The sprockets stayed fast.
Just as the machine was ready for test
bad weather set in. It had been disagree-
ably cold for several weeks, so cold that
we could scarcely work on the machine
for some days. But now we began to
have rain and snow, and a wind of 25 to
30 miles blew for several days from the
north. While we were being delayed by
the weather we arranged a mechanism to
measure automatically the duration of a
flight from the time the machine started
to move forward to the time it stopped,
the distance traveled through the air in
that time, and the number of revolutions
made by the motor and propeller. A
stop watch took the time; an anemo-
meter measured the air traveled
through; and a counter took the number
of revolutions made by the propellers.
The watch anemometer and revolution
counter were all automatically started
and stopped simultaneously. From data
thus obtained we expected to prove or
disprove the accuracy of our propeller
calculations.
On November 28, while giving the mo-
tor a run indoors, we thought we again
saw something wrong with one of the
propeller shafts. On stopping the motor
we discovered that one of the tubular
shafts had cracked!
Immediate preparation was made for
returning to Dayton to build another set
of shafts. We decided to abandon the
use of tubes, as they did not afford
enough spring to take up the shocks of
premature or missed explosions of the
motor. Solid tool-steel shafts of smaller
diameter tJian the tubes previouslj' used
were decided upon. These would allow
a certain amount of spring. The tubular
shafts were many times stronger than
would have been necessary to transmit
the power of our motor if the strains up-
on them had been unifonn. But the
large hollow shafts had no spring in them
to absorb the unequal strains.
Wilbur remained in camp while I went
to get the new shafts. I did not get back
to camp again till Friday, the 11th of De-
cember. Saturday afternoon the ma-
chine was again ready for trial, but the
wind was so light a start could not have
been made from level ground with the
run of only sixty feet permitted by our
monorail track. Nor was there enough
time before dark to take the machine to
one of the hills, where, by placing the
track on a steep incline, sufficient speed
could be secured for starting in calm air.
Monday, December 14, was a beautiful
day, but there was not enough wind to
enable a start to be made from the level
ground about camp. We therefore de-
cided to attempt a flight from the side of
the big Kill Devil Hill. We had arranged
with the members of the Kill Devil Hill
Life Saving Station, which was located a
little over a mile from our camp, to in-
form them when we were ready to make
the first trial of the machine. We were
soon joined by J. T. Daniels, Robert
Westcott, Thomas Beachem, W. S. Dough
and Uncle Benny O'Neal, of the station,
who helped us get the machine to the hill,
a quarter mile away. We laid the track
150 feet up the side of the hill on a 9-de-
gree slope. With the slope of the track,
the thrust of the propellers and the ma-
chine starting directly into the wind, we
did not anticipate any ti'ouble in getting
i«
THE
EARLY
HISTORY
O F
THE
AIRPLANE
up flying speed on the 60-foot monorail
track. But we did not feel certain the
operator could keep the machine bal-
anced on the track.
When the machine had been fastened
with a wire to the track, so that it could
not start until released by the operator,
and the motor had been run to make sure
that it was in condition, we tossed up a
coin to decide who should have the first
trial. Wilbur won. I took a position at
one of the wings, intending to help bal-
ance the machine as it ran down the
track. But when the restraining wire
was slipped, the machine started off so
quickly I could stay with it only a few
feet. After a 35 to 40-foot run it lifted
from the rail. But it was allowed to turn
up too much. It climbed a few feet,
stalled, ^nd then settled to the ground
near the foot of the hill, 105 feet below.
My stop watch showed that it had been
in the air just 3l^ seconds. In landing
the left wing touched first. The machine
swung around, dug the skids into the
sand and broke one of them. Several
other parts were also broken, but the
damage to the machine was not serious.
While the test had shown nothing as to
whether the power of the motor was suf-
ficient to keep the machine up, since the
landing was made many feet below the
starting point, the experiment had dem-
onstrated that the method adopted for
launching the machine was a safe and
practical one. On the whole, we were
much pleased.
Two days were consumed in making
repairs, and the machine was not ready
again till late in the afternoon of the
16th. While we had it out on the track
in front of the building, making the final
adjustments, a stranger came along.
After looking at the machine a few sec-
onds he inquired what it was. When we
told him it was a flying machine he asked
whether we intended to fly it. We said
we did, as soon as we had a suitable wind.
He looked at it several minutes longer
and then, wishing to be courteous, re-
marked that it looked as if it would fly,
if it had a "suitable wind." We were
much amused, for, no doubt, he had in
mind the recent 75-mile gale when he re-
peated our words, "a suitable wind!"
During the night of December 16,
1903, a strong cold wind blew from the
north. When we arose on the morning
of the 17th, the puddles of water, which
had been standing about camp since the
recent rains, were covered with ice. The
wind had a velocity of 10 to 12 meters per
second (22 to 27 miles an hour). We
thought it would die down before long,
and so remained indoors the early part
of the morning. But when ten o'clock
arrived, and the wind was as brisk as
ever, we decided that we had better get
the machine out and attempt a flight.
We hung out the signal for the men of
the life saving station. We thought that
by facing the tlyer into a strong wind,
there ought to be no trouble in launch-
ing it from the level ground about camp.
We realized the difficulties of flying in
so high a wind, but estimated that the
added dangers in flight would be partly
compensated for by the slower speed in
landing.
We laid the track on a smooth stretch
of ground about one hundred feet north
of the new building. The biting cold
wind made work difficult, and we had to
warm up frequently in our living room,
where we had a good fire in an impro-
vised stove made of a large carbide can.
By the time afl was ready, J. T. Daniels,
W. S. Dough and A. D. Etheridge, mem-
bers of the Kill Devil Life Saving Station;
W. C. Brinkley, of Manleo, and Johnny
Moore, a boy from Nag's Head, had ar-
rived.
We had a "Richards" hand anemo-
meter with which we measured the ve-
»
THE
EARLY
HISTORY
O F
THE
AIRPLANE
locity of the wind. , Measurements made
just before starting the first flight showed
velocities of 11 to 12 meters per second,
or 24 to 27 miles per hour. Measure-
ments made just before the last flight
gave between 9 and 10 meters per sec-
ond. One made just after showed a little
over 8 meters. The records of the Gov-
ernment Weather Bureau at Kitty Hawk
gave the velocity of the wind between the
hours of 10:30 and 12 o'clock, the time
during which the four flights were made,
as averaging 27 miles at the time of the
first flight and 24 miles at the time of the
last.
***** -0
Wilbur, having used his turn in the
unsuccessful attempt on the 14th, the
right to the first trial now belonged to
me. After running the motor a few min-
utes to heat it up, I released the wire that
held the machine to the track, and the
machine started forward into the wind.
Wilbur ran at the side of the machine,
holding the wing to balance it on the
track. Unlike the start on the 14th, made
in a calm, the machine, facing a 27-mile
wind, started verj' slowly. Wilbur was
able to stay with it till it lifted from the
track after a forty-foot run. One of the
life saving men snapped the camera for
us, taking a picture just as the machine
had reached the end of the track and had
risen to a height of about two feet. The
slow forward speed of the machine over
the ground is clearly shown in the pic-
lure by Wilbur's attitude. He stayed
along beside the machine witliout any
effort.
The course of the flight up and down
was exceedingly erratic, partly due to the
irregularity of the air, and partly to lack
of experience in handUng this machine.
The control of the front rudder was difQ-
cult on account of its being balanced too
near the center. This gave it a tendency
to turn itself when started; so that it
turned too far on one side and then too
far on the other. As a result the machine
would rise suddenly to about ten feet,
and then as suddenly dart for the ground.
A sudden dart when a little over a hun-
dred feet from the end of the track, or a
little over 120 feet from the point at
which it rose into the air, ended the flight.
As the velocity of the wind was over 35
feet per second and the speed of the ma-
chine against this wind ten feet per sec-
ond, the speed of the machine relative to
the air was over 45 feet per second, and
the length of the flight was equivalent to
a flight of 540 feet made in calm air.
This flight lasted only 12 seconds, but it
was nevertheless the first in the history
of the world in which a machine carrying
a man had raised itself by its own power
into the air in full flight, had sailed for-
ward without reduction of speed, and
had finally landed at a point as high as
that from which it started.
******
At twenty minutes after eleven Wilbur
tarted on the second flight. The course
of this flight was much like that of the
first, very much up and down. The
speed over the ground was somewhat
faster than that of the first flight, due to
the lesser wind. The duration of the
flight was less than a second longer than
the first, but the distance covered was
about seventy-five feet greater.
Twenty minutes later the third flight
started. This one was steadier than the
first one an hour before. I was proceed-
ing along pretty well when a sudden gust
from the right lifted the machine up
twelve to fifteen feet and turned it up
sidewise in an alarming manner. It be-
gan sliding ofi" to the left. I warped the
wings to try to recover the lateral bal-
ance and at the same time pointed the
machine down to reach the ground as
quickly as possible. The lateral control
was more effective than I had imagined
14
THE
EARLY
HISTORY
O F
THE
AIRPLANE
and before I reached the ground the right
wing was lower than the left and struck
first. The time of this flight was fifteen
seconds and the distance over the ground
a little over 200 feet.
Wilbur started the fourth and last
flight at just 12 o'clock. The first few
hundred feet were up and down as be-
fore, but by the time three hundred feet
had been covered, the machine was un-
der much better control. The course for
the next four or five hundred feet had
but little undulation. However, when
out about eight hundred feet the machine
began pitching again, and, in one of its
starts downward, struck the ground.
The distance over the ground was meas-
ured and found to be 852 feet; the time
of the flight 59 seconds. The frame sup-
porting the front rudder was badly
broken, but the main part of the ma-
chine was not injured at all. We esti-
mated that the machine could be put in
condition for flight again in a day or two.
While we were standing about discuss-
ing this last flight, a sudden strong gust
of wind struck the machine and began
to turn it over. Everybody made a rush
for it. Wilbur, who was at one end,
seized it in front, Mr. Daniels and I, who
were behind, tried to stop it behind, tried
to stop it by holding to the rear uprights.
All our efforts were vain. The machine
rolled over and over. Daniels, who had
retained his grip, was carried along with
it, and was thrown about head over heels
inside of the machine. Fortunately he
was not seriously injured, though badly
bruised in falling about against the mo-
tor, chain guides, etc. The ribs in the
surfaces of the machine were broken, the
motor injured and the chain guides badly
bent, so that all possibility of further
flights with it for that year were at an
end.
u
Some Aeronauticdl Experiments
By Wilbur Wright
HE difficulties which obstruct
the pathway to success in fly-
ing machine construction are
of three general classes: (1)
Those which relate to the construction of
the sustaining wings. (2) Those which
relate to the generation and application
of the power required to drive the ma-
chine through the air. (3) Those relat-
ing to the balancing and steering of the
machine after it is actually in flight. Of
these difficulties two are already to a cer-
tain extent solved. Men already know
how to construct wings or aeroplanes
which, when driven through air at suffi-
cient speed, will not only sustain the
weight of the wings themselves, but also
that of the engine, and of the engineer as
well. Men also know how to build en-
gines and screws of sufficient lightness
and power to drive these planes at sus-
taining speed. As long ago as 1893 a ma-
chine weighing 8,000 lbs. demonstrated
its power both to lift itself from the
ground and to maintain a speed of from
30 to 40 miles per hour; but it came to
grief in an accidental free flight, owing
to the inability of the operators to bal-
ance and steer it properly. This inability
to balance and steer still confronts stu-
dents of the flying problem, although
nearly ten years have passed. When this
one feature has been worked out the age
of flying machines will have arrived, for
all other difficulties are of minor im-
portance.
The person who merely watches the
flight of a bird gathers the impression
that the bird has nothing to think of but
the flapping of its wings. As a matter of
fact, this is a very small part of its men-
tal labour. Even to mention all the
things the bird must constantly keep in
mind in order to fly securely through the
ail' would take a very considerable trea-
tise. If I take a piece of paper,
and after placing it parallel with the
ground, quickly let it fall, it will not set-
tle steadily down as a staid, sensible piece
of paper ought to do, but it insists on con-
travening every recognized rule of de-
corum, turning over and darting hither
and thither in the most erratic manner,
much after the style of an untrained
horse. Yet this is the style of steed that
men must learn to manage before flying
can become an everyday sport. The bird
has learned this art of equilibrium, and
learned it so thoroughly that its skill is
not apparent to our sight. We only learn
to appreciate it when we try to imitate it.
Now, there are two ways of learning how
to ride a fractious horse: one is to get on
him and learn by actual practice how
each motion and trick may be best met;
the other is to sit on a fence and watch
the beast awhile, and then retire to the
house and at leisure figure out the best
way of overcoming his jumps and kicks.
The latter system is the safest; but the
former, on the whole, turns out the larger
porportion of good riders. It is very
much the same in learning to ride a flying
machine; if you are looking for perfect
safety you will do well to sit on a fence
and watch the birds; but if you really
wish to learn you must mount a machine
and become acquainted with its tricks
by actual trial.
******
My own active interest in aeronautical
problems dates back to the death of
Lilienthal in 1896. The brief notice of
his death which appeared in the tele-
graphic news at that time aroused a pas-
sive interest which had existed from my
i«
THE
EARLY
HISTORY
O F
THE
AIRPLANE
childhood, and led me to take down from
the shelves of our home library a book
on "Animal Mechanism," by Prof.
Marey, which I had already read several
times. From this I was led to read more
modern works, and as my brother soon
became equally interested with myself,
we soon passed from the reading to the
thinking, and finally to the working
stage. It seemed to us that the main
reason why the problem had remained so
long unsolved was that no one had been
able to obtain any adequate practice. We
figured that Lilienthal in five years of
time had spent only about five hours in
actual gliding through the air. The won-
der was not that he had done so little, but
that he had accomplished so much. It
would not be considered at all safe for a
bicycle rider to attempt to ride through
a crowded city street after only five
hours' practice, spread out in bits of ten
seconds each over a period of five years;
yet Lilienthal with this brief practice was
remarkably successful in meeting the
fluctuations and eddies of wind gusts.
We thought that if some method could be
found by which it would be possible to
practice by the hour instead of by the
second there would be hope of advancing
the solution of a very difficult problem.
It seemed feasible to do this by building
a machine which would be sustained at
a speed of 18 miles per hour, and then
finding a locality where winds of this ve-
locity were common. With these condi-
tions a rope attached to the machine to
keep it from floating backward would
answer very nearly the same purpose as
a propeller driven by a motor, and it
would be possible to practice by the hour,
and without any serious danger, as it
would not be necessary to rise far from
the ground, and the machine would not
have any forward motion at all. We
found, according to the accepted tables of
air pressures on curved surfaces, that a
machine spreading 200 square feet of
wing surface would be sufficient for our
purpose, and that places could easily be
found along the Atlantic coast where
winds of 16 to 25 miles were not at aU
uncommon. When the winds were low
it was our plan to glide from the tops of
sand hills, and when they were sufficient-
ly strong to use a rope for our motor and
fly over one spot. Our next work was to
draw up the plan for a suitable machine.
After much study we finally concluded
that tails were a source of trouble rather
than of assistance, and therefore we de-
cided to dispense with them altogether.
It seemed reasonable that if the body of
the operator could be placed in a horizon-
tal position instead of the upright, as in
the machines of Lilienthal, Pitcher and
Chanute, the wind resistance could be
very materially reduced, since only one
square foot instead of five would be ex-
posed. As a full half-horse-power could
be saved by this change, we arranged to
try at least the horizontal position. Then
the method of control used by Lilienthal,
which consisted in shifting the body, did
not seem quite as quick or effective as the
case required; so, after long study, we
contrived a system consisting of two
large surfaces on the Chanute double-
deck plan, and a smaller surface placed
a short distance in front of the main sur-
faces in such a position that the action of
the wind upon it would counterbalance
the effect of the travel of the center of
pressure on the main surfaces. Thus
changes in the direction and velocity of
the wind would have little disturbing ef-
fect, and the operator would be required
to attend only to the steering of the ma-
chine, which was to be effected by curv-
ing the foi'ward surface up or down.
The lateral equilibrium and the steering
to right or left was to be attained by a
peculiar torsion of the main surfaces,
which was equivalent to presenting one
»
THE
EARLY
HISTORY
O F
THE
AIRPLANE
end of the wings at a greater angle than
the other. In the main frame a few
changes were also made in the details of
construction and trussing employed by
Mr. Chanute. The most important of
these were: ( 1 ) The moving of the for-
ward main cross-piece of the frame to
the extreme front edge; (2) the encasing
in the cloth of all cross-pieces and ribs of
the surfaces; (3) a rearrangement of the
wires used in trussing the two surfaces
together, which rendered it possible to
tighten all the wires by simply shortening
two of them.
With these plans we proceeded in the
summer of 1900 to Kitty Hawk, North
Carolina, a little settlement located on
the strip of land that separates Albemarle
Sound from the Atlantic Ocean. Owing
to the impossibility of obtaining suitable
material for a 200-square-foot machine,
we were compelled to make it only 165
square feet in area, which, according to
the Lilienthal tables, would be supported
at an angle of three degrees in a wind of
about 21 miles per hour. On the very
day that the machine was completed the
wind blew from 25 to 30 miles per hour,
and we took it out for a trial as a kite.
We found that while it was supported
with a man on it in a wind of about 25
miles, its angle was much nearer 20 de-
grees than three degrees. Even in gusts
of 30 miles the angle of incidence did not
get as low as three degiees, although the
wind at this speed has more than twice
the lifting power of a 21-mile wind. As
winds of 30 miles per hour are not plen-
tiful on clear days, it was at once evident
that our plan of practicing by the hour,
day after day, would have to be post-
poned. Our system of twisting the sur-
faces to regulate the lateral balance was
tried and found to be much more effec-
tive than shifting the operator's body.
On subsequent days, when the wind was
too light to support the machine with a
man on it, we tested it as a kite, working
the rudders by cords reaching to the
ground. The results were very satisfac-
tory, yet we were well aware that this
method of testing is never wholly con-
vincing until the results are confirmed by
actual gliding experience.
We then turned our attention to mak-
ing a series of actual measurements of
the lift and drift of the machine under
various loads. So far as we were aware,
this had never previously been done with
any full-size machine. The results ob-
tained were most astonishing, for it ap-
peared that the total horizontal pull of
the machine, wliile sustaining a weight
of 52 lbs., was only 8.5 lbs., which was
less than had previously been estimated
for head resistance of the framing alone.
Making allowance for the weight carried,
it appeared that the head resistance of
the framing was but little more than 50
per cent, of the amount which Mr.
Chanute had estimated as the head re-
sistance of the framing of his machine.
On the other hand, it appeared sadly de-
ficient in lifting power as compared with
the calculated lift of curved surfaces of
its size. This deficiency we supposed
might be due to one or more of the fol-
lowing causes: — (1) That the depth of
the curvature of our surfaces was insuf-
ficient, being only about one in 22, in-
stead of one in 12. (2) That the cloth
used in our wings was not sufficiently air-
tight. (3) That the Lilienthal tables
might themselves be somewhat in error.
We decided to arrange our machine for
u
THE
EARLY
HISTORY
O F
THE
AIRPLANE
the following year so that the depth of
the curvature of its surfaces could be
varied at will and its covering air-
proofed.
Our attention was next turned to glid-
ing, but no hill suitable for the purpose
could be found near our camp at Kitty
Hawk. This compelled us to take the ma-
chine to a point four miles south, where
the Kill Devil sand hill rises from the flat
sand to a height of more than 100 feet.
Its main slope is toward the northeast,
and has an inclination of 10 degrees. On
the day of our arrival the wind blew
about 25 miles an hour, and as we had
had no experience at all in gliding, we
deemed it unsafe to attempt to leave the
ground. But on the day following, the
wind having subsided to 14 miles per
hour, we made about a dozen glides. It
had been the original intention that the
operator should run with the machine to
obtain initial velocity, and assume the
horizontal position only after the ma-
chine was in free flight. When it came
time to land he was to resume the up-
right position and alight on his feet,
after the style of previous gliding ex-
periments. But in actual trial we found
it much better to employ the help of two
assistants in starting, which the peculiar
form of our machine enabled us readily
to do; and in landing we found that it was
entirely practicable to land while still re-
clining in a horizontal position upon the
machine. Although the landings were
made while moving at speeds of more
than 20 miles an hour, neither machine
nor operator suffered any injury. The
slope of the hiU was 9.5 deg., or a drop
of one foot in six. We found that after
attaining a speed of about 25 to 30 miles
with reference to the wind, or 10 to 15
miles over the ground, the machine not
only glided parallel to the slope of the
hill, but greatly increased its speed, thus
indicating its ability to glide on a some-
what less angle than 9.5 deg., when we
should feel it safe to rise higher from the
surface. The control of the machine
proved even better than we had dared to
expect, responding quickly to the slight-
est motion of the rudder. With these
glides our experiments for the year 1900
closed. Although the hours and hours
of practice we had hoped to obtain finally
dwindled down to about two minutes,
we were very much pleased with the gen-
eral results of the trip, for, setting out as
we did with almost revolutionary the-
ories on many points and an entirely un-
tried form of machine, we considered it
quite a point to be able to return without
having our pet theories completely
knocked on the head by the hard logic
of experience, and our own brains
dashed out in the bargain. Everything
seemed to us to confirm the correctness
of our original opinions — (1) that prac-
tice is the key to the secret of flying; (2)
that it is practicable to assume the hori-
zontal position; (3) that a smaller sur-
face set at a negative angle in front of
the main bearing surfaces, or wings, will
largely counteract the effect of the fore
and aft travel of the center of pressure;
(4) that steering up and down can be at-
tained with a rudder without moving the
position of the operator's body; (5) that
twisting the wings so as to present their
ends to the wind at different angles is a
more prompt and efficient way of main-
taining lateral equilibrium than that em-
ployed in shifting the body of the oper-
ator of the machine.
When the time came to design our new
machine for 1901 we decided to make it
exactly like the previous machine in the-
ory and method of operation. But as the
former machine was not able to support
the weight of the operator when flown
as a kite, except in very high winds and
at very large angles of incidence, we de-
cided to increase its lifting power. Ac-
is
THE
EARLY
HISTORY
O F
THE
AIRPLANE
corcjingly, the curvature of the surfaces
was increased to one in 12, to confonn to
the shape on which LiUenthal's table was
based, and to be on the safe side we de-
cided also to increase the area of the ma-
chine from 165 square feet to 308 square
feet, although so large a machine had
never before been deemed controllable.
The Lilienthal machine had an area of
151 square feet; that of Pilcher, 165
square feet; and the Chanute double-
decker, 134 square feet. As our system
of control consisted in a manipulation of
the surfaces themselves instead of shift-
ing the operator's body, we hoped that
the new machine would be controllable,
notwithstanding its great size. Accord-
ing to calculations, it would obtain sup-
port in a wind of 17 miles per hour with
an angle of incidence of only three de-
grees.
Our experience of the previous year
having shown the necessity of a suitable
building for housing the machine, we
erected a cheap frame building, 16 feet
wide, 25 feet long, and 7 feet high at the
eaves. As our machine was 22 feet wide,
14 feet long (including the rudder), and
about 6 feet high, it was not necessary to
take the machine apart in any way in or-
der to house it. Both ends of the build-
ing, except the gable parts, were made
into doors which hinged above, so that
when opened they formed an awning at
each end and left an entrance the full
width of the building. We went into
camp about the middle of July, and were
soon joined by Mr. E. C. Huftaker, of
Tennessee, an experienced aeronautical
investigator in the employ of Mr. Cha-
nute, by whom his services were kindly
loaned, and by Dr. A. G. Spratt, of Penn-
sylvania, a young man who has made
some valuable investigations of the
properties of variously curved surfaces
and the travel of the center of pressure
thereon. Early in August Mr. Chanute
came down from Chicago to witness our
experiments, and spent a week in camp
with us. These gentlemen, with my
brother and myself, formed our camping
party, but in addition we had in many
of our experiments the valuable assist-
ance of Mr. W. J. Tate and Mr. Dan Tate,
of Kitty Hawk.
******
It had been our intention when build-
ing the machine to do most of the
experimenting in the following manner:
— When the wind blew 17 miles an hour,
or more, we would attach a rope to the
machine and let it rise as a kite with the
operator upon it. When it should reach
a proper height the operator would cast
off the rope and glide down to the ground
just as from the top of a hill. In this way
we would be saved the trouble of carry-
ing the machine uphill after each glide,
and could make at least 10 glides in the
time required for one in the other way.
But when we came to try it we found that
a wind of 17 miles, as measured by Rich-
ards' anemometer, instead of sustaining
the machine with its operator, a total
weight of 240 lbs., at an angle of inci-
dence of three degrees, in reality would
not sustain the machine alone — 100 lbs.
— at this angle. Its lifting capacity
seemed scarcely one-third of the calcu-
lated amount. In order to make sure that
this was not due to the porosity of the
cloth, we constructed two small experi-
mental surfaces of equal size, one of
which was aii'-proofed and the other left
in its natural state; but we could detect
no difference in their lifting powers.
80
THE
EARLY
HISTORY
O F
THE
AIRPLANE
For a time we were led to suspect that the
lift of curved surfaces little exceeded
that of planes of the same size, but fur-
ther investigation and experiment led to
the opinion that (1) the anemometer
used by us over-recorded the true ve-
locity of the wind by nearly 15 per cent.;
12) that the well-known Smeaton coefJi-
[ent of .005 V ^ for the wind pressure at
0 degrees is probably too great by at
least 20 per cent.; (3) that Lilienthal's es-
timate that the pressure on a curved sur-
face having an angle of incidence of
three degrees equals .545 of the pressure
at 90 degrees is too large, being narly 50
per cent, greater than very recent experi-
ments of our own with a special pressure
testing machine indicate; (4) that the su-
perposition of the surfaces somewhat re-
duced the lift per square foot, as com-
pared with a single surface of equal area.
In gliding experiments, however, the
amount of lift is of less relative import-
ance than the ratio of lift to drift, as this
alone decides the angle of gliding de-
scent. In a plane the pressure is always
perpendicular to the surface, and the
ratio of lift to drift is therefore the same
as that of the cosine to the sine of the
angle of incidence. But in curved sur-
faces a verj^ remarkable situation is
found. The pressure, ijistead of being
uniformly normal to the chord of the arc,
is usually inclined considerably in front
of the perpendicular. The result is that
the lift is greater and the drift less than
if the pressure were normal. Lilienthal
was the first to discover this exceedingly
though our measurements differ consid-
erably from those of Lilienthal. While
important fact, which is fully set forth
in his book, "Bird Flight the Basis of the
Flying Art," but owing to some errors in
the methods he used in making measure-
ments, question was raised by other in-
vestigators not onlj' as to the accuracy of
Ais figures, but even as to the existence of
any tangential force at all. Our experi-
ments confirm the existence of this force,
at Kitty Hawk we spent much time in
measuring the horizontal pressure on
our unloaded machine at various angles
of incidence. We found that at 13 de-
grees the horizontal pressure was about
23 lbs. This included not only the drift
proper, or horizontal component of the
pressure on the side of the surface, but
also the head resistance of the framing
as well. The weight of the machine at
the time of this test was about 108 lbs.
Now, if the pressure had been normal to
the chord of the surface, the drift proper
would have been to the lift (108 lbs.) as
the sine of 13 degrees is to the cosine of
13 degrees, or^?^^^ = 24 + lbs.; but
this slightly exceeds the total pull of 23
lbs. on our scales. Therefore, it is evi-
dent that the average pressure on the sur-
face, instead of being normal to the
chord, was so far inclined toward the
front that all the head resistance of fram-
ing and wires used in the construction
was more than overcome. In a wind of
14 miles per hour resistance is by no
means a negligible factor, so that tang-
ential is evidently a force of considerable
value. In a higher wind, which sustained
the machine at an angle of 10 degrees, the
pull on the scales was 18 lbs. With the
pressure normal to the chord the drift
proper would have been
.17 X 98
.98
17
lbs., so that, although the higher wind ve-
locity must have caused an increase in
THE
EARLY
HISTORY
O F
THE
AIRPLANE
the head resistance, the tangential force
still came within one pound of overcom-
ing it. After our return from Kitty
Hawk we began a series of experiments
to accurately detennine the amount and
direction of the pressure produced on
curved surfaces when acted upon by
winds at the various angles from zero to
90 degrees. These experhnents are not
yet concluded, but in general they sup-
port Lilienthal in the claim that the
curves give pressures more favorable in
amount and direction than planes; but
we find marked differences in the exact
values, especially at angles below 10 de-
grees. We were unable to obtain direct
measurements of the horizontal pres-
sures of the machine with the operator
on board, but by comparing the distance
traveled in gliding with the vertical fall,
it was easily calculated that at a speed of
24 miles per hour the total horizontal re-
sistance of our machine when bearing
the operator, amounted to 40 lbs., which
is equivalent to about 2 1/3 horse-power.
It must not be supposed, however, that a
motor developing this power would be
sufficient to drive a man-bearing ma-
chine. The extra weight of the motor
would require either a larger machine,
higher speed, or a greater angle of inci-
dence in order to support it, and there-
fore more power. It is probable, how-
ever, that an engine of six horse-power,
weighing 100 lbs., would answer the pur-
pose. Such an engine is entirely practi-
cable. Indeed, working motors of one-
half this weight per horse-power (9 lbs.
per horse-power) have been constructed
by several different builders. Increasing
the speed of our machine from 24 to 33
miles per hour reduced the total horizon-
tal pressure from 40 to about 35 lbs. This
was quite an advantage in gliding, as it
made it possible to sail about 15 per cent,
further with a given drop. However, it
would be of little or no advantage in re-
ducing the size of the motor in a power-
driven machine, because the lessened
thrust would be counter-balanced by the
increased speed per minute. Some years
ago Professor Langley called attention to
the great economy of tlirust which might
be obtained by using very high speeds,
and from this many were led to suppose
that high speed was essential to success
in a motor-driven machine. But the
economy to which Professor Langley
called attention was in foot-pounds per
mile of travel, not in foot pounds per
minute. It is the foot-pounds per min-
ute that fixes the size of the motor. The
probability is that the first flying ma-
chines will have a relatively low speed,
perhaps not much exceeding 20 miles per
hour, but the problem of increasing the
speed will be much simpler in some re-
spects than that of increasing the speed
of a steamboat; for, whereas in the latter
case the size of the engine must increase
as the cube of the speed, in the flying ma-
chine, until extremely high speeds are
reached, the capacity of the motor in-
creases in less than simple ratio; and
there is even a decrease in the fuel con-
sumption per mile of travel. In other
words, to double the speed of a steam-
ship (and the same is true of the balloon
type of airship) eight times the engine
and boiler capacity would be required,
and four times the fuel consumption per
mile of travel; while a flying machine
would require engines of less than
double the size, and there would be an
actual decrease in the fuel consumption
per mile of travel. But looking at the
matter conversely, the great disadvan-
tage of the flying machine is apparent;
8S
THE
EARLY
HISTORY
O F
THE
AIRPLANE
for in the latter no flight at all is possible
unless the proportion of horse-power to
flying capacity is very high; but on the
other hand a steamship is a mechanical
uccess if its ratio of horse-power to ton-
nage is insignificant. A flying machine
that would fly at a speed of 50 miles an
hour with engines of 1 ,000 horsepower
would not be upheld by its wings at all at
a speed of less than 25 miles an hour, and
nothing less than 500 horse-power could
drive it at this speed. But a boat which
could make 40 miles per hour with en-
gines of 1,000 horse-power would still
move four miles an hour even if the en-
gines were reduced to one horse-power.
The problems of land and water travel
were solved in the nineteenth century,
because it was possible to begin with
small achievements and gradually work
up to our present success. The flying
prolem was left over to the twentieth
century, because in this case the art must
be highly developed before any flight of
any considerable duration at aU can be
obtained.
However, there is another way of fly-
ing which requires no artificial motor,
and many workers believe that success
will first come by this road. I refer to
the soaring flight, by which the machine
is permanently sustained in the air by
the same means that are employed by
soaring birds. They spread their wings
to the wind, and sail by the hour, with no
perceptible exertion beyond that re-
quired to balance and steer themselves.
What sustains them is not definitely
known, though it is almost certain that it
is a rising current of air. But whether
it be a rising current or something else,
it is as well able to support a flying ma-
chine as a bird, if man once learns the art
of utilizing it. In gliding experiments it
has long been known that the rate of ver-
tical descent is very much retarded, and
the duration of the flight greatly pro-
longed, if a strong wind blows up the face
of the hill parallel to its surface. Our
machine, when gliding in still air, has a
rate of vertical descent of nearly six feet
per second, while in a wind blowing 26
miles per hour up a steep hill we made
glides in which the rate of descent was
less than two feet per second. And dur-
ing the larger part of this time, while the
machine remained exactly in the rising
current, there was no descent at all, but
even a slight rise. If the operator had
had sufficient skill to keep himself from
passing beyond the rising current he
would have been sustained indefinitely
at a higher point than that from which
he started.
******
In looking over our experiments of
the past two years, with models and full-
size machines, the following points stand
out with clearness: —
1. That the lifting power of a large
machine, held stationary in a wind at a
small distance from the earth, is much
less than the Lilienthal table and our own
laboratory experiments would lead us to
expect. When the machine is moved
through the air, as in gliding, the discrep-
ancy seems much less marked.
2. That the ratio of drift to lift in
well-balanced surfaces is less at angles
of incidence of five degrees to 12 de-
grees than at an angle of three degrees.
3. That in arched surfaces the center
of pressure at 90 degrees is near the cen-
ter of the surface, but moves slowly f or-
23
THE
EARLY
HISTORY
O F
THE
AIRPLANE
ward as the angle becomes less, till a
critical angle varying with the shape and
depth of the curve is reached, after which
it moves rapidly toward the rear till the
angle of no lift is found.
4. That with similar conditions large
surfaces may be controlled with not
much greater difficulty than small ones,
if the control is effected by manipulation
of the surfaces themselves, rather than
by a movement of the body of the oper-
ator.
5. That the head resistances of the
framing can be brought to a point much
below that usually estimated as neces-
sary.
6. That tails, both vertical and hori-
zontal, may with safety be eliminated in
gliding and other flying experiments.
7. That a horizontal position of the
operator's body may be assumed without
excessive danger, and thus the head re-
sistance reduced to about one-fifth that
of the upright position.
8. That a pair of superposed, or tan-
dem, surfaces has less lift in proportion
to drift than either surface separately,
even after making allowance for weight
and head resistance of the connections.
1
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